<template>
  <div class="spec-preview">
    <img v-if="skuImageList[currentIndex]" :src="skuImageList[currentIndex].imgUrl" />
    <div class="event" @mousemove="move"></div>
    <div class="mask" ref="mask"></div>
    <div class="big">
      <img v-if="skuImageList[currentIndex]" ref="bigImage"
           :src="skuImageList[currentIndex].imgUrl" />
    </div>
  </div>
</template>

<script>
  import {mapGetters} from "vuex";
  export default {
    name: "Zoom",
    data(){
      return {
          currentIndex:0
      }
    },
    computed:{
        ...mapGetters(["skuImageList"])
    },
    methods:{
        move(event){
          //代表  maskDiv最终要产生的位移
          const maskDiv = this.$refs.mask;
          const bigImage = this.$refs.bigImage;
          let left = 0;
          let top = 0;

          //maskDiv的尺寸
          //触发mousemove事件时 鼠标距离event.div paddingbox的偏移量
          const {offsetX,offsetY} = event;
          const width = maskDiv.offsetWidth;
          //计算left & top的实时值
          left  = offsetX - width/2;
          top  = offsetY - width/2;

          //处理一下left & top的边界情况
          left < 0 ? left = 0 : "";
          left > width ? left = width : "";
          top < 0 ? top = 0 : "";
          top > width ? top = width : "";

          //获取mask dom节点
          maskDiv.style.left = left + "px";
          maskDiv.style.top = top + "px";
          bigImage.style.left = -2*left + "px";
          bigImage.style.top = -2*top + "px";
        }
    },
    mounted(){
        this.$bus.$on("getIndexForZoom",(index)=>{
            this.currentIndex = index;
        })
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }
    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }
    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>